A hydrogen fuel cell is an electro-chemical device that includes an anode and a cathode with an electrolyte therebetween. The anode receives a fuel such as hydrogen gas and the cathode receives an oxidant such as oxygen or air. Several fuel cells are typically combined in a fuel cell stack to generate a desired amount of power. A typical fuel cell stack for a vehicle may include several hundred individual cells. Typically, the fluid is caused to flow through the stack by a compressor. Oxygen not consumed in the stack is expelled as a cathode exhaust gas that may include water as a stack by-product.
A fuel cell stack includes a wet end adapted to receive the fuel, oxidizer, and cooling fluids, and a dry having an insulation end plate unit. When producing a fuel cell stack, it may be necessary to pressurize the system to prepare the fuel cell stack for operation. The fuel cell stack is typically pressurized to test for leaks, and to ensure that the stack will function efficiently. Over pressurization of the fuel cell stack is undesirable.
It has been a continuing challenge to provide an efficient and cost effective fuel cell stack which militates against an over pressurization during production, testing, or operation. Space in and round the fuel cell stack is extremely limited and valued, especially in vehicular applications.
Prior art fuel cell stacks include unit cells and separators. Each fuel cell typically includes a solid polymer electrolyte membrane having a pair of electrode catalysts disposed on opposing surfaces. The fuel cell further includes a pair of collectors, each having a rigid body, and in contact with respective electrode catalysts. Each of the separators comprises a pair of pressure generating plates defining therebetween a pressure chamber, to which pressurized fluid is introduced. The pressure generating plates are deformable by the pressurized fluid, and are pressed against adjacent collectors.
Other prior art fuel cell stacks use pressure relief valves that include a housing having a passageway extending therethrough and include an inlet, an outlet, and a membrane extending across the passageway between the inlet and the outlet. The membrane permits the passage of gas at a first pressure, inhibits the passage of fluid at a first pressure, and permits the passage of liquid at a second pressure greater that the first pressure. The pressure relief valves may also include a check valve for inhibiting the passage of gas from the outlet to the inlet. The pressure relief valves are suitably employed in fuel cell systems such as in cooling systems for fuel cells. The pressure relief valves may be used in cooling systems to release gases or liquids therefrom in an overpressure condition.
It would be desirable to produce a fuel cell stack assembly having an integrated pressure relief valve to militate against an over pressurization of the stack assembly.